Hi Adam:
Just a shot in the dark here, but: I wonder if the root cause of the problem is that the 1.6 liter engine in your car is working 'relatively hard' to maintain the lower speeds (speeds below 60 MPH) when you have the cruise control engaged, and as a result, the engine is a bit sluggish to respond to small amounts of increased fuel flow, and as a result, the sends a bigger squirt of increased fuel flow (as a second attempt, so to speak) when the car does not begin to recapture the target speed fast enough after the first small amount of increased fuel is provided in response to the drop in vehicle speed.
I suspect that VW has rigged the and the transmission in such a way as to maximize fuel economy when cruising at steady speeds below 60 MPH. The transmission is probably in the highest possible gear, which means that the engine is turning quite slowly (slowly relative to a more typical freeway speed of 70 or 75 MPH). At that slower engine speed, the engine is likely not operating at optimum speed for producing torque, or horsepower, or whatever is needed to quickly increase the vehicle speed when just a small increase in fuel flow is scheduled. Consequently, the cruise control system schedules another, more substantial increase in fuel flow to correct the slower than set-point vehicle speed, and it is that second bump-up in fuel flow that you are feeling.
My VW has a 420 HP 6.0 litre 12 cylinder engine in it, and when the cruise control is engaged at lower vehicle speeds, it will very smoothly and very efficiently maintain the cruise control set-speed regardless of whatever hindrances it may encounter (hills, gusting headwinds, standing water, etc.). The only difference between my car and yours is that my VW has a large surplus of horsepower available and torque available when the engine is operating at slow speeds, and (perhaps) your car does not.
I've seen the same kind of behaviour with aircraft autothrottle systems - if you command a flight level change at a high weight on a hot day, you will feel a noticeable surge of power to maintain the set speed during the climb. But, at lower set speeds, lightly loaded, on a cold day, you hardly hear or feel anything when a FLCH is commanded.
Michael